L98 Mod Help!
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Junior Member
Joined: Feb 2010
Posts: 42
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From: Denver, CO
Car: 86 Z28
Engine: 350TPI
Transmission: 700R4 lookin for shift kit
Axle/Gears: 3.23???
L98 Mod Help!
I was planning to swap out my 305tpi for a 406 carb, I pulled the engine, long story short i want to save that engine for another project. so with that i want to purchase a 350tpi from hawks. correct me if i am wrong but stock 350 tpi makes about 250hp? with that engine, what mods can you guys help me with to get the l98 engine to about 300 to 320 hp??? details would help alot.
thanks in advance
thanks in advance
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
The 245 net HP rating is about 285-295 gross HP (the way crate engines are "rated").
So, are you talking about getting 300-320 HP out of an L98 instead of getting a crate engine that's rated at that, or taking the 245 net rating up to 300-320?
So, are you talking about getting 300-320 HP out of an L98 instead of getting a crate engine that's rated at that, or taking the 245 net rating up to 300-320?
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Then you need about 1 gross HP per cubic inch.
Check Atilla's build sticky for one that matches your combo and goals.
Check Atilla's build sticky for one that matches your combo and goals.
Thread Starter
Junior Member
Joined: Feb 2010
Posts: 42
Likes: 0
From: Denver, CO
Car: 86 Z28
Engine: 350TPI
Transmission: 700R4 lookin for shift kit
Axle/Gears: 3.23???
Re: L98 Mod Help!
i want to keep to the stock tpi, maybe get bigger injectors and heads and cam with choppy idle. do you think that will put me around 300? and i will check that out
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Pretty much backwards. The first stock thing to change is the TPI hardware. Then you can think about cam, injectors, and heads.
Exhaust has to be the very first, though.
Choppy idle and TPI shouldn't be used in the same sentence.
Exhaust has to be the very first, though.
Choppy idle and TPI shouldn't be used in the same sentence.
Thread Starter
Junior Member
Joined: Feb 2010
Posts: 42
Likes: 0
From: Denver, CO
Car: 86 Z28
Engine: 350TPI
Transmission: 700R4 lookin for shift kit
Axle/Gears: 3.23???
Re: L98 Mod Help!
thank you, i took alook and now i have an idea of what direction to go towards. i have some research to do. appreciate the help
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From: Northern Utah
Car: seeking '90.5-'92 'bird hardtop
Engine: several
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Re: L98 Mod Help!
882 heads on a 400 is a huge mistake all by itself. Even with really good porting, big valves, and so on, they're still maybe 220 cfm at 0.500" lift. Certainly no better.
If you want to do it, then get some AFR 180 heads.
If you can't afford such heads, then just stick to a 350.
If you do buy the good heads, then plan on TPiS base and runners, 52 mm TB, ported plenum, and so on.
If you want to do it, then get some AFR 180 heads.
If you can't afford such heads, then just stick to a 350.
If you do buy the good heads, then plan on TPiS base and runners, 52 mm TB, ported plenum, and so on.
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